The invention relates to magnetic cored solenoid type line sensor systems, and more particularly, to magnetic cored solenoid type sensor systems capable of discriminating between magnetic and strain stimuli.
Perimeter monitoring or protection systems using magnetic cored solenoid type transducer line sensors are well known in the art. In these systems, the magnetic cored solenoid line transducer is buried under the ground around the area that is to be protected against intrusion. Such systems are commonly called perimeter detectors. The transducer will produce output signals when subjected to a magnetic stimulus, a strain stimulus or when subjected to both a magnetic and strain stimuli. The output of the transducer is coupled to suitable electronic circuitry that produces an alarm signal whenever the transducer produces output signals in response to magnetic and/or strain stimuli. Thus, if any intruder that provides magnetic and/or strain stimuli to the transducer approaches or crosses the transducer, an alarm signal is produced by the system.
While the typical prior art systems described above detect any intrusion into the area surrounded by the line transducer, these prior art systems do not discriminate between a magnetic stimulus and a strain stimulus. Thus, while the person monitoring the system is made aware of the fact that an intrusion has occurred, he does not know the nature of the intrusion. That is, he does not know if the alarm was caused by a strain stimulus, a magnetic stimulus, or by both magnetic and strain stimuli. The system of this invention provides a magnetic cored solenoid line transducer system that discriminates between magnetic and strain stimuli. With the apparatus of this invention, the person monitoring the perimeter detection system is made aware of the nature of the intrusion with respect to magnetic and strain stimuli. That is, the system of this invention provides a first output for magnetic stimulus, a second output for strain stimulus and both the first output and the second output when the transducer is subject to both magnetic and strain stimuli. In this manner discrimination between magnetic and strain stimuli is provided with the system of this invention.